Health workers near Mbandaka, in the Democratic Republic of Congo, in June. An outbreak there was declared over last week, only to be followed by a new one 1,500 miles away.CreditCreditJunior D. Kannah/Agence France-Presse — Getty Images

The Ebola virus has struck again in the Democratic Republic of Congo and has killed at least 20 people, the country’s Health Ministry reported Wednesday, just a week after officials announced the end of an Ebola outbreak 1,550 miles away.

The latest outbreak was the 10th time that Ebola, a contagious affliction that can quickly spread out of control, has menaced the Democratic Republic of Congo, a sprawling Central African country about twice the size of Texas. The virus, which causes fevers and fatal hemorrhaging, first appeared in the country in 1976.

The health minister, Dr. Oly Ilunga Kalenga, said in a statement that the authorities in North Kivu Province had notified his ministry on Saturday of 26 suspected cases of Ebola, including the 20 deaths. Samples from the six survivors were analyzed on Tuesday in Kinshasa, the capital, and four tested positive for the virus.

“The Democratic Republic of Congo is facing a new epidemic,” the minister’s statement said.

In April, Ebola afflicted an area of Equator Province that included Mbandaka, a river port with more than one million inhabitants. The location raised alarms that the virus could infect other parts of Central Africa.

That outbreak, which killed at least 33 people, was contained within a few months and was officially declared over on July 24.

Public health officials considered the response to that outbreak a notable success, aided in part by the use of a new Ebola vaccine and aggressive action by the World Health Organization, which quickly sent aid and helped identify who had been exposed to prevent the disease from spreading further.

Dr. Tedros Adhanom Ghebreyesus, the director general of the World Health Organization, said on Twitter that it already was moving staff members and supplies to North Kivu. He said that Ebola was a constant threat in the Democratic Republic of Congo and that “we will fight this one as we did the last.”

Dr. Ilunga said in his statement that “at this stage, there is no indication that these two epidemics, separated by more than 2,500 kilometers, are related.”

He said the ministry was “taking all necessary steps to rapidly and effectively contain this new Ebola virus disease outbreak.”

“This new cluster is occurring in an environment which is very different from where we were operating,” Dr. Peter Salama, the World Health Organization’s deputy director general, said in a statement. “This is an active conflict zone. The major barrier will be safely accessing the affected population.”

Julien Paluku, the governor of North Kivu Province, took to Twitter to spread the word. “Urgent!!!! Urgent!!!!!” he wrote in sharing the ministry’s announcement, while calling for “calm and prudence.”

Health officials have paid extraordinary attention to stopping any Ebola outbreak in its early phases, after a catastrophic Ebola epidemic in West Africa three years ago killed more than 11,000 people. An initially slow international response was partly responsible for its spread, and the economic cost to the three afflicted countries — Guinea, Sierra Leone and Liberia — was more than $2.2 billion, according to the World Bank.

Steve Wembe contributed reporting from Nairobi, Kenya, and Satoshi Sugiyama from New York.

A version of this article appears in print on , on Page A10 of the New York edition with the headline: Ebola Strikes Central Africa Once Again. Order Reprints | Today’s Paper | Subscribe